1. Field of the Invention
The invention relates to preparations for activating hemocytes of bivalves for pearl production used in nucleus insertion operation in culture pearl production, and a method for producing pearls using such a preparation. The invention provides a useful and new technique for productivity enhancement in the industry of pearl culture.
More specifically, preparations obtained by the invention activate hemocytes at the wound site by the nucleus insertion operation on bivalves for pearl production, and thereby promote tissue growth of a section of the mantle of a donor, which is another pearl oyster, (this section is hereinafter referred to as a "piece") after this piece is inserted together with the nucleus to form a good pearl sac around the nucleus. Therefore, by use of the preparations, the pearl production yield is improved.
The technique of culturing of pearls was first established in Japan and developed as an important industry peculiar to Japan. This technique has recently spread abroad, for example, to Southeast Asia.
The nucleus insertion operation, which is an important step in production of cultured pearls, is carried out by incising the gonad part of a bivalve such as pearl oyster (Pinctada martensii), goldlip (Pinctada maxima) or pearly freshwater mussel (Hyriopsis schleqeli), and inserting therein in mutually close contact (1) a spherical nucleus prepared by processing a shell, for example, a thick shell of a freshwater shellfish from the USA, and (2) a square piece prepared by cutting out a 2 to 3 mm square mantle part of a donor.
Granular hemocytes (granular blood cells) and agranular hemocytes (agranular blood cells) exist in a floating state as so-called blood cells in the humor of shellfishes, and are considered to play a role similar to the role of macrophages and lymphocytes in vertebrates. These cell groups are called hemocytes or wandering cells in invertebrates, and the humor thereof is thought of as blood.
Hemocytes, particularly agranular hemocytes, assemble along the inside of the incised part wherein the nucleus is inserted, by nucleus insertion operation, and a sheet formed of the hemocytes is formed on the surface of the nucleus. The tissue cells of the piece proliferate by division along this sheet, gradually surround the nucleus to form a pearl sac, and secrete nacreous substantia inside the pearl sac, whereby a nacreous layer is formed on the surface of the nucleus. The object of the piece insertion is to form a pearl sac so as to cause nacreous substantia to be secreted on the surface of this nucleus.
As will be understood from the foregoing, the more rapidly the hemocytes assemble at the topical site of the nucleus insertion operation and the sooner the operation wound heals, the higher is the likelihood of a pearl sac being formed. At the same time, the rate of pearl production is increased and productivity is enhanced. It is important in pearl culturing to carry out these steps at low cost and with good reproducibility, and development of techniques enabling this has been greatly desired.
2. Prior Art
Many factors have an influence on pearl quality. For example, lack of close contact of the piece with the nucleus at the time of the nucleus insertion operation may become a cause of formation of a shiradama (a nucleus lacking nacreous layer) or a kuzudama (a nucleus only partially coated with nacreous substantia), neither of which has any commercial value. For facilitating confirmation of this close contact, it has long been the practice to dye the piece using a diluent of mercurochrome, actizol, Eosine Y, food red or the like with sea water.
Further, various attempts have been made at producing pearls of a high quality by utilizing a pharmacological effect. For example, yolk lecithin, light sensitive dye agents, antibiotics, etc. may be used for the purpose. Yolk lecithin is said to activate the cells, light-sensitive dye agents have physiological activities such as a cell-activating activity, an activity accelerating healing of wound and a sterilizing activity, and antibiotics are used mainly for utilizing their sterilizing and bacteriostatic activities.
As practical examples of a preparation containing a light-sensitive dye agent as a main component, there can be mentioned Praxin (manufactured by KK Nippon Kanko Shikiso Kenkyusho) wherein Pratonin and Neoxin are compounded, and Minol No. 1 (manufactured by KK Nippon Kanko Shikiso Kenkyusho). As antibiotics, aureomycin, chlorotetracycline, etc. are used. Further, azomine (Heiwa Seiyaku KK), which uses an azo dye, has been marketed. Azomine is a preparation consisting of sodium sulfothielazonaphtoldisulfonic acid and p-aminophenylsulfonamide as azo dyes which provide sterilizing or antiphlogistic activities, compounded together with sodium salt of chondroitin sulfate or taurine as a cell-activating agent. In addition to providing pharmacalogical effect, it also dyes the piece with the azo dye.
All of these preparations now on the market are diluted to predetermined concentration with sea water at the time of use and are then. supplied onto the piece, for example, by using a dropper to drop the dilution on the piece cut into smaller pieces, applying the dilution with a brush or the like onto a piece cut into smaller pieces, or immersing the whole piece in the dilution before it is cut.
Examples of known effective techniques are cited below. These are taken from Uemoto, et al., "Shinju no Yoshoku" (Pearl Culture) published by Nippon Shinju Shinko Kai, Tokyo, PP 29-30 (1987). Takaoka (1957) is reported as saying that an effect was brought about by methionine and that Illuminol RII gave a slightly higher emergence rate of pearls of good quality. Yamashita et al. (1961) are reported as saying that when Pratonin or Neoxin is used as a light-sensitive dye, the resulting pearls have few CH carrier, of flaws. Their view is based on only 2 or 3 shellfishes and is hard to evaluate due to the small number of experimental examples. Miyauchi (1962) is reported as saying that Eosine Y was more harmless and brought about higher emergence rate of higher grade pearls than mercurochrome, and that the emergence rate of higher grade pearls became higher, the rate of shiradama production became lower and further, the death rate after nucleus insertion was decreased by dyeing the piece with a mixed solution of chlorotetracycline and mercurochrome and further immersing the shellfish and an apparatus for inserting a nucleus in a chlorotetracycline solution before and after nucleus insertion. Machii (1965) is reported as having concluded that yolk lecithin, aureomycin and pincchloron were effective because better results, as respectively compared with the control group, were obtained in 12 groups among 20 test groups in case of yolk lecithin, in 8 groups among 14 groups in case of Aureomycin and 19 groups among 33 groups in case of pincchloron in experiments carried out several times using 100 to 300 shellfishes per group. However, Machii is also said to have noted that the rate of production of kizudama (a nucleus missing some of its nacreous substantia coating or having a protuberance(s); limited commercial value) and kuzudama became higher in many groups. Further, Machii (1967) is said to have found that using yolk lecithin and pincchloron together, and using yolk lecithin and aureomycin together were both effective, and to have stated of that in such cases, though the number of kizudama and kuzudama were not decreased, the problem of increase in the number of kuzudama due to phytotoxicity was eliminated.
Further, there is a disclosure that the productivity of good quality pearls was higher in pearls of the azomine-treated group as harvested than in pearls of the control group as harvested, but it is not certain whether the disclosure is credible.
From the poor results obtained by their actual use in the field, these preparations cannot be expected to increase productivity substantially, and thus enhancement of the yield of good quality pearls is desired. It is necessary for formation of a pearl sac that tissue division of the inserted piece occur regularly, and it is a prerequisite for this that many of the agranular blood cells in the shellfish body assemble around the inserted nucleus and smoothly surround the nucleus. Thus, it is necessary to form a good pearl sac by activating the hemocytes and accelerating the activity of the piece.